These guys were washed up on the beach in mid-Oct - Purple Bubble-raft Snails. If you want to see one in the water, there is a beautiful shot here on the Australian Geographic webpage.
These snail shells aren't terrible big, maybe the size of a 10 c piece but that brilliant purple colour leapt off the sand at me. And the texture of the shell is quite gorgeous, which I tried to capture.
The Australian Geographic article says that all snails start out as male and switch to female as they age.
The males have no penis, they just fertilise the female by excreting sperm in the female's direction. She then births live miniature purple snails.
The bubble raft is a mucous bubble, which the snail produces, that hardens and the snail attaches to it. If it breaks, the snail sinks and dies.
They float on the ocean, feeding on blue bottles and velellas. No wonder they all washed up together then!
Purple snails aren't just found in Australia, but all tropical and temperate oceans.
A nice way to travel the world - blown along on a bubble, riding the wild seas, and if you lose the bubble, you sink and die. Or you get washed up on the shore and die as you bake in the sun.
On that cheery note, I'll leave you. Have a great week!